Doesn't really look much like a snail, does it? They are filter feeders and suck water in, filter it and then expel it (as this one is seen doing.) The Balinese decorate their shrines with the bottoms of pop cans as accents, much like these snails decorate a coral head.

2003:09:09 10:10:57
Island: Bali
Dive Site: Padangbai
Speed: 1/30 sec
Aperture: f8.0
ISO: 64
Exposure Compensation: 0.0
Exposure Program: Program
Focal Length: 7 mm
Flash: